High performance plastics, in particular polysulfone polymers, thanks to their attractive properties, are currently used for the manufacture of several parts and articles intended to deliver outstanding mechanical properties in severe conditions.
Among processing technologies used for the manufacture of final parts, said polymers are often extrusion molded; more particularly, for the manufacture of sheets and profiles, molten material is extruded from a die and pulled out through appropriate rolls or dies so as to achieve required thickness. Melt strength, i.e. tensile strength of the polymer when in molten state so as to avoid melt fractures and failures, is thus a key property. High molecular weight plastics, in particular high molecular weight polysulfones, are generally understood to comply with these requirements; nevertheless, processability of these high molecular weight materials is relatively poor, limiting throughputs and production rates.
While processing temperature might improve melt flowability, these conditions may lead to degradation and black speck formation.
Traditional flow modifiers, such as MFA, PFA, PTFE or LLDPE, generally require high concentrations to be effective: at these high concentrations, these additives are not compatible in the blend, so that non-homogenous mixtures are obtained, whose performance are negatively affected. Also, certain additives (e.g. LLDPE) are not thermally stable in processing conditions of said high performance plastics.
In the past, perfluoropolyether-based additives have already been suggested for high performances plastics. In particular, JP 63264672 (NTN-RULON INDUSTRIES) Jan. 11, 1988 discloses a lubricating compositions for synthetic resins (e.g. polysulfone resins) comprising a perfluoropolyether compound, for improvement of wear/abrasion resistance. Also, U.S. Pat. No. 7,355,816 (MAXTOR CORPORATION) Aug. 4, 2008 discloses thermoplastic polymer compositions based on high performance materials (e.g. polyetherimides, polyphenylensulfides, polysufones) comprising PTFE and/or perfluoropolyether lubricants for reducing wear.
Nevertheless, these perfluoropolyether additives were not investigated for their performances as melt flow modifiers and were not proven to provide any of such effects in taught compositions.
There is thus a current shortfall in the art for flow modifiers for high performance plastics which can override above mentioned problems, which are able to withstand processing temperatures without undergoing degradation phenomena, and which can effectively improve processability and melt flow behaviour of said plastics, without negatively affecting their mechanical performances.